1. Field of Invention
The present invention pertains generally to autostereoscopic three-dimensional (3D) displays, and relates more particularly to methods and structures for reducing crosstalk between viewing windows.
2. Description of Related Art
Traditionally, stereoscopic, i.e. 3D, images are created by aid of headgear that control viewing of separate left and right stereoscopic images by the left and right eyes, respectively, of a viewer. Each of the left and right images displays the same scene from slightly shifted viewing angles that closely match the viewing angles of a viewer's eyes. By conveying the separate left and right images to the viewers left and right eyes with viewing angles closely matching each eye's normal viewing angle, an illusion of a 3-Dimensional, i.e. 3D, display is created for the viewer.
Although this approach is effective, the required headgear (such as head-mounted displays or glasses with specialized lenses for rejecting specific angle views) makes this approach cumbersome. An alternative to using headgear is to use autostereoscopic displays, i.e. specialized displays that display select images at specific view angles such that only by viewing the display at a specific view angle can one view a select image. Theses specific view angles are typically termed “viewing windows”.
Autostereoscopic displays use special light directing devices to create separate viewing windows in the user's space, which allow the user to see 3D images without glasses. Since the designated viewing windows form a viewing space that is significantly larger than the size of the human eye, users can move their heads freely as long as their eyes are within the viewing space.
Current stereoscopic methods used to produce the viewing windows include parallel-barrier-based displays and lenticular-based displays.
Parallel-barrier displays use light blocking to produce viewing windows, but this approach results in a dimmer image since only a small amount of light emitted from each pixel passes through the barrier window. Overlap of viewing areas causes crosstalk causing one eye to see the image intended for the other eye. When crosstalk is significant, one cannot perceive the stereo effect or cannot perceive it correctly. Parallel-barrier displays also use small apertures that can cause diffraction, particularly as the display resolution is increased. As the display resolution increases, the barrier aperture size is decreased, which causes more severe diffraction effects. Parallel-barrier displays divide the resolution of the original display by the number of views such that to display n views, the resolution of the individual view becomes 1/n of the original display resolution. Parallel-barrier displays suffer from dark pixel lines due to each view seeing only one pixel column out of n associated with one barrier window.
Lenticular-based displays offer some improvements over parallel-barrier-based displays. Lenticular-based displays offer higher resolution compared with the barrier slits of parallel-barrier-based displays, but they are generally more difficult and costly to make due to the need for high quality lenticular sheets. Generally, the quality of the lenticular-based display is directly related to the quality of the lenticular sheet used in the display. Aligning a lenticular sheet with a display also requires significant effort. Although lenticular-based displays offer benefits over parallel-barrier-based displays, lenticular-based displays also suffer from crosstalk between view windows, dark line problem, limited resolution, and limit number of viewing windows.
Another solution is to use retro-reflective, multi-view 3D displays, which use projectors to create multiple viewing windows. These displays create distinct view windows by means of special reflective properties of the display. However, these displays typically have a limited view view-area, which limits the area in which the 3D effect can be perceived. Another limitation of typical retro-reflective displays is that they do not lend themselves to the creation of wide-view-screen displays.